In the related art, a robot such as an industrial robot has a link mechanism corresponding to a joint of a creature. The link mechanism is controlled by calculating an arm position and an arm angle thereof at all times (e.g., see Japanese Unexamined Patent Application Publication No. 2005-121371 (Patent Document 1)). In particular, when a robot is used as a part of production apparatuses, the robot needs to precisely pick up a workpiece flowing on its production line, and measure for safety is required such that a part of the robot, which is a rigid body, does not come into contact with a person. Thus, it is necessary to perform relatively-complicated calculation that takes into consideration the position and the interference range of each arm.
Regarding the contents of calculation for control in such a robot, a three-dimensional coordinate of a target operation position is converted into an absolute coordinate with respect to a predetermined reference point, and the deviation between the coordinate and an actual position detected by a sensor or the like is calculated at all times, thereby generating a control command for a driver such as a motor.
Specifically, for example, in the case of a robot having six degrees of freedom, multiplication of a 4×4 matrix needs to be performed six times for once calculating a position of an arm end. Further, multiplication of a 4×4 inverse matrix needs to be performed six times for once generating a control command from a deviation with respect to a target operation position.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2005-121371
As described above, even in a general industrial robot having six degrees of freedom, an amount of calculation required for performing control thereof is huge, but there is a limit on high-speed processing. Further, when an actuator having 15 degrees of freedom, which represents a finger of a person, is attempted to be realized, it is assumed that calculation processing for a control command diverges and hence cannot be executed. In addition, when an array structure in which a plurality of actuators are connected in series or in parallel is used, calculation therefor becomes complicated. Therefore, there is a limit on existing control methods that require accurate calculation of an arm position as in an existing robot.
On the other hand, recently, an artificial actuator focusing on a mechanism of a muscle of a creature, namely, an actuator called an artificial muscle, has been attracting attention. In an actual creature, a muscle called an active muscle and a muscle called an antagonistic muscle cooperate to from a joint or the like. For example, when moving a joint, one of the muscles contracts while the other muscle is maintained in a relaxation state. The muscle in the relaxation state changes its expansion and contraction state with a small force. Thus, the amount of work generated due to the contraction of the muscle is used almost for moving the joint (external work).
It is assumed that use of such an array structure that approximates a joint of a creature and in which a plurality of actuators are combined, allows realization of a more flexible actuator system.
However, when the same control method as for an existing industrial robot is used for such an actuator system, there is a problem that its performance cannot be sufficiently exerted.